The long-term objective of this research is to understand how the cerebral cortex acquires and stores information, which can lead to neurobiological interventions in maladaptive thought and behavior, and impaired learning in development and aging. Although the cerebral cortex is by far the largest part of the human brain and is a major structure that subserves learning and memory, it has been neglected because of the need for animal models of cortical memory. However, recent studies have established that the auditory cortex develops memory-like changes in the frequency tuning of individual cells during fear learning, termed "receptive field plasticity". This neural plasticity is associative, highly specific, rapidly acquired and retained indefinitely, like major forms of human memory. Cortical control of subcortical fear centers is known but not understood. The specific aims of this project are to determine the nature and extent to which the overall functional organization of the auditory cortex is involved in fear learning and memory. The specific goal of this research project is to provide the first comprehensive investigation of the extent to which learning modifies the spatial representation of behaviorally relevant acoustic frequencies in the primary auditory cortex. Guinea pigs will be trained with pure tones in habituation, sensitization, classical, and instrumental conditioning. Further, the development and long term retention (weeks), and the degree of reversibility of plasticity will be delineated. The neurobiological bases of fear conditioning, which is basic to acquired anxieties, phobias and other behavioral pathologies, requires direct investigation of cellular mechanisms because pharmacological treatments can reduce the elicitation and expression of these emotions but not eliminate their cause.